Tweak the code add add some unit tests

Author: ColdPaleLight

shell/platform/android/io/flutter/embedding/android/FlutterActivityAndFragmentDelegate.java

@@ -74,7 +74,7 @@
   // to this FlutterActivityAndFragmentDelegate.
   @NonNull private Host host;
   @Nullable private FlutterEngine flutterEngine;
-  @Nullable private FlutterView flutterView;
+  @VisibleForTesting @Nullable FlutterView flutterView;
   @Nullable private PlatformPlugin platformPlugin;
   @VisibleForTesting @Nullable OnPreDrawListener activePreDrawListener;
   private boolean isFlutterEngineFromHost;

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -1420,17 +1420,17 @@ public void autofill(SparseArray<AutofillValue> values) {
     textInputPlugin.autofill(values);
   }
 
-  // TODO add comment
+  // Invoke this from {@code FlutterActivityAndFragmentDelegate#onStart()}
   /* package */ void onStart() {
-    if (flutterSurfaceView != null && flutterSurfaceView.getParent() == null) {
-      addView(flutterSurfaceView);
+    if (flutterSurfaceView != null) {
+      flutterSurfaceView.setVisibility(View.VISIBLE);
     }
   }
 
-  // TODO add comment
+  // Invoke this from {@code FlutterActivityAndFragmentDelegate#onStop()}
   /* package */ void onStop() {
-    if (flutterSurfaceView != null && flutterSurfaceView.getParent() != null) {
-      removeView(flutterSurfaceView);
+    if (flutterSurfaceView != null) {
+      flutterSurfaceView.setVisibility(View.GONE);
     }
   }
 

shell/platform/android/test/io/flutter/embedding/android/FlutterActivityAndFragmentDelegateTest.java

@@ -983,6 +983,24 @@ public void itThrowsWhenDelayingTheFirstDrawAndUsingATextureView() {
         });
   }
 
+  @Test
+  public void itNotifiesFlutterViewWhenOnStartAndOnStop() {
+    // ---- Test setup ----
+    // Create the real object that we're testing.
+    FlutterActivityAndFragmentDelegate delegate = new FlutterActivityAndFragmentDelegate(mockHost);
+
+    // --- Execute the behavior under test ---
+    delegate.onAttach(RuntimeEnvironment.application);
+    delegate.onCreateView(null, null, null, 0, true);
+    delegate.flutterView = mock(FlutterView.class);
+    delegate.onStart();
+    // Verify that the onStart of flutterView was called.
+    verify(delegate.flutterView, times(1)).onStart();
+    delegate.onStop();
+    // Verify that the onStop of flutterView was called.
+    verify(delegate.flutterView, times(1)).onStop();
+  }
+
   @Test
   public void itDoesNotDelayTheFirstDrawWhenRequestedAndWithAProvidedSplashScreen() {
     when(mockHost.provideSplashScreen())

shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java

@@ -687,6 +687,18 @@ public void itRegistersAndUnregistersToWindowManager() {
     verify(windowInfoRepo, times(1)).removeWindowLayoutInfoListener(any());
   }
 
+  @Test
+  public void itChangesSurfaceViewVisibilityWhenOnStartAndOnStop() {
+    Context context = Robolectric.setupActivity(Activity.class);
+    FlutterView flutterView = spy(new FlutterView(context));
+    FlutterSurfaceView flutterSurfaceView = (FlutterSurfaceView) flutterView.renderSurface;
+    assertEquals(View.VISIBLE, flutterSurfaceView.getVisibility());
+    flutterView.onStop();
+    assertEquals(View.GONE, flutterSurfaceView.getVisibility());
+    flutterView.onStart();
+    assertEquals(View.VISIBLE, flutterSurfaceView.getVisibility());
+  }
+
   @Test
   public void itSendsHingeDisplayFeatureToFlutter() {
     Context context = Robolectric.setupActivity(Activity.class);